Kittens at 5 and a half weeks

They are growing so rapidly and are very active. 3 of them will eat from a bowl but the 4th one will not. We have tried everything we can to get her to eat but nothing doing. I suppose the mother will have to cut her off to make her eat from the bowl. They can climb up a cat tree and can climb up on the couch. There are two boys and two girls. The black one is a boy and is the biggest of the litter. They were born on June 1st.We can no longer keep them in the bathroom where we have had them so they pretty much have the run of the house. They can climb out in an instant. All four of them are using the litter box, but their mother does not. we will be starting to look for homes for at least 2 of them and maybe 3, I guess we have to get the last one eating first. We want to keep 1 at least.